Apparatus for detecting residual quantity of toners

Abstract

Disclosed is a toner residual quantity detecting apparatus for detecting a residual quantity of toners in a developing unit. This toner residual quantity detecting apparatus has a temperature sensor, provided in the bottom of the developing unit, for generating an output proportional to a detected temperature and a detecting circuit for detecting the toner residual quantity from the output of the temperature sensor. This temperature sensor detects a difference between temperatures when covered with the toners and when not covered with the toners, thereby detecting the toner residual quantity.

What is claimed is: 
     
       1. A developing apparatus for developing a latent image on a latent image carrier, comprising: a supplying means for supplying toners to said latent image carrier;   a toner residual quantity detecting means for detecting a toner residual quantity in said developing apparatus for housing toners, wherein said toner residual quantity detecting means comprises: a first temperature detecting means, provided in a bottom portion of said developing apparatus, for generating an output proportional to a detected temperature; and   a detecting circuit means for detecting sad toner residual quantity from said output of said first temperature detecting means.     
     
     
       2. The developing apparatus according to claim 1, wherein said first temperature detecting means is a heating type temperature detector. 
     
     
       3. The developing apparatus according to claim 2, wherein said first temperature detecting means is a thermistor. 
     
     
       4. The developing apparatus according to claim 3, wherein said detecting circuit means includes a second temperature detecting means for making a comparison with said output of said first temperature detecting means. 
     
     
       5. The developing apparatus according to claim 4, wherein said second temperature detecting means is connected in series to said first temperature detecting means, and said detecting circuit means further includes comparing means for comparing an electrical potential of a connecting point between said first temperature detecting means and said second temperature detecting means with a reference electrical potential.   
     
     
       6. The developing apparatus according to claim 3, further comprising a second temperature detecting means provided in a toner-always-existing position of said developing unit. 
     
     
       7. The developing apparatus according to claim 6, wherein said first temperature detecting means exhibits a temperature detecting characteristic similar to a temperature detecting characteristic of said second temperature detecting means. 
     
     
       8. The developing apparatus according to claim 3, further comprising a heating body provided in said developing unit. 
     
     
       9. The developing apparatus according to claim 2, wherein said detecting circuit means includes a second temperature detecting means for making a comparison with said output of said first temperature detecting means. 
     
     
       10. The developing apparatus according to claim 9, wherein said second temperature detecting means is connected in series to said first temperature detecting means, and said detecting circuit means further includes comparing means for comparing an electrical potential of a connecting point between said first temperature detecting means and said second temperature detecting means with a reference electrical potential.   
     
     
       11. The developing apparatus according to claim 2, further comprising a second temperature detecting means provided in a toner-always-existing position of said developing unit. 
     
     
       12. The developing apparatus according to claim 11, wherein said first temperature detecting means exhibits a temperature detecting characteristic similar to a temperature detecting characteristic of said second temperature detecting means. 
     
     
       13. The developing apparatus according to claim 2, further comprising a heating body provided in said developing unit. 
     
     
       14. The developing apparatus according to claim 13, further comprising means for causing said heating body to periodically emit heat. 
     
     
       15. The developing apparatus according to claim 1, wherein said detecting circuit includes a second temperature detecting means for making a comparison with said output of said temperature detecting means. 
     
     
       16. The developing apparatus according to claim 4, wherein said first temperature detecting means exhibits temperature detecting characteristic similar to a temperature detecting characteristic of said second temperature detecting means. 
     
     
       17. The developing apparatus according to claim 15, wherein said second temperature detecting means is connected in series to said first temperature detecting means, and said detecting circuit means further includes comparing means for comparing an electrical potential of a connecting point between said first temperature detecting means and said second temperature detecting means with a reference electrical potential.   
     
     
       18. The developing apparatus according to claim 1, further comprising a second temperature detecting means provided in a toner-always-existing position of said developing unit. 
     
     
       19. The developing apparatus according to claim 18, wherein said first temperature detecting means exhibits a temperature detecting characteristic similar to a temperature detecting characteristic of said second temperature detecting means. 
     
     
       20. The developing apparatus according to claim 1, further comprising a heating body provided in said developing unit. 
     
     
       21. The developing apparatus according to claim 20, further comprising means for causing said heating body to periodically emit heat.